The present invention relates to an image reading apparatus, a document conveying apparatus and a composite apparatus.
In an image reading apparatus, if a rotation speed of a conveying roller for conveying a document changes, a conveying speed of the document which is being read may also change. This may result in occurrence of distortion in a read image.
Therefore, Japanese Application Publication No. H10-145552 discloses an image reading apparatus that detects a conveying speed of a document, creates distortion correction data based on a change rate of the detected conveying speed, and corrects a read image using the distortion correction data.
However, in general, an image is read at constant intervals, i.e., a predetermined number of lines are thinned out. Therefore, if the conveying speed of the document changes during the reading of the document, the number of lines which are thinned out may increase or decrease. Therefore, even if the correction of the read image is performed as described above, a read image may be different from an original image.
Therefore, there is a demand for technology capable of preventing occurrence of distortion in a read image due to a change in a conveying speed of a document.